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Bad to leave unused "wallwart" transformer plugged in?

Discussion in 'General Electronics' started by Noozer, Aug 21, 2004.

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  1. Noozer

    Noozer Guest

    Just wondering...

    Is it OK to leave the AC adapters used by many gadgets plugged in while it
    isn't connected to anything? For example, AC->DC charger for a cellphone
    left plugged under my desk with the end of the cord on the desk in a handy,
    out of the way location.

    I assume that an AC->AC adapter should be OK, but an AC->DC might have
    problems since it has the rectifier and filter caps always trickling a bit
    of current through them. Even worse would be the switching supply of a
    laptop when the laptop was elsewhere.

    Other than the obvious electrical spikes that could damage anything, is it
    bad to leave these things plugged in?
  2. CFoley1064

    CFoley1064 Guest

    Subject: Bad to leave unused "wallwart" transformer plugged in?
    Nearly all cellphone chargers have switching regulators built in. They're a
    lot more susceptible to damage from the "obvious electrical spikes" than the
    old transformer/rectifier-capacitor adapters of yore.

    Somewhat more important, though, is the business of "hot plugging" the
    cellphone into a powered-up charger. With a switch, you have basically one
    "turn on event" which occurs over a 10 ms period. When you're plugging in a
    hot charger, your "turn on event" is repeated on-off-on cycles over several
    hundred milliseconds. That may damage the switcher or, more likely, the phone.

    If you've got one available, use a power strip with a switch accessible from
    your desk to turn on the charger after plugging it in, and turn it off before
    you unplug. I personally think it's worth the price of a power strip for the
    improved reliability.

    Good luck
  3. Ken Taylor

    Ken Taylor Guest

    While I agree with you in principle, I have to say I don't think that cell
    phones for one are without power management circuitry and software. The IC's
    are commonplace for this task and you would note the delay between plugging
    the phone into its charging cradle and the 'beep' when it goes on charge.

  4. Karl Uppiano

    Karl Uppiano Guest

    Lazy and reckless soul that I am, I always leave wall-warts plugged in -- AC
    or DC. It's just more convenient, and wall-warts are relatively cheap, and
    besides, I've never, ever, had one fail.
  5. It's OK to leave them pluged in. Millions do it every day without
    problem. The chances of them failing are very remote.
    Of course they are chewing latent power, so it's environmentally
    unfriendly not to mention that it's costing you money to leave them
    plugged in 24/7
    Be careful of the connector end of the lead though, make sure they
    can't short on anything.

    Dave :)
  6. SumGie

    SumGie Guest

    Hmm... read some of the other replies... here's something that the others
    seem to have missed:

    No, it won't hurt the wall wart to be plugged in. It'll just get, and stay,
    a little warm to the touch, but won't get damaged.


    If it's warm to the touch, that's evidence that it is using power. Your
    electric bill will go up. Not by much, but the whole time it's plugged in
    and not being used, you're actually paying to use it as a room heater... A
    very inefficient room heater. Wasteful. Not dangerous.
  7. TrAI

    TrAI Guest

    I would think it would be 100% efficient in its conversion of its idle
    electricity usage to heat, so it wouldn't be an inefficient heater or
    wasteful(it wouldn't be able to heat a room by itself, but that is
    more about power, not efficiency). Actually, as long as you live a
    place where the temperature outside is below comfortable room
    temperature, no energy the devices you have inside uses is really
    wasted, as it will all help heat your rooms. Thats one of the
    paradoxes of the commercials for energy saving lamps(you know, the
    fluorescent bulb things), yes they are more efficient, but unless you
    live in a hot place or use active cooling, the energy saved by using
    more efficient light sources will have to be used by heaters to heat
    the place.
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